METHOD TO INFER ABOUT THE NUCLEAR UHE COSMIC-RAY COMPOSITION FROM THEEAS LATERAL DEVELOPMENT

Results from a detailed Monte-Carlo simulation for electromagnetic and hadronic cascades in the atmosphere, generated by primary gamma-rays, p, O and Fe are provided in the primary energy range 10(12)-10(16)eV for vertical incident showers. In the simulation of the Extensive Air Showers (EAS) development, the CORSIKA (COsmic Ray SImulator for KAsca de) code has been used to perform a full simulation of the electromagn etic and hadronic interactions. The lateral development of the electro magnetic component, for both, pure electromagnetic and hadronic cascad es have been deeply investigated and the NKG-type functions have been fitted to the lateral developments, to determine the lateral age param eters. Results on the variation of the shower size with the lateral ag e parameter and primary energy are obtained, as well as fluctuations o n shower size at maximum development depth of the EAS and at mountain altitude (X = 800 gcm(-2)). The main aim of this work is to obtain an accurate procedure to discriminate the nuclear composition of the UHE cosmic rays from the gamma rays background. We also seek to provide re lations to interpret the experimental data, for those who do not have detailed simulation calculations available and also to provide materia l for a full and deep comparison of air shower Monte-Carlo codes.